On manual or automatic application of paints onto objects, a sub-stream of the paint, which generally contains both solids and solvent and/or binder, is not applied onto the object. In specialist circles, this sub-stream is known as “overspray”. The overspray is entrained by the air stream in the spray booth and sent for separation.
In particular in installations with relatively high paint consumption, for example in installations for painting vehicle bodies, wet separation systems are preferably used. In commercially known wet separators, water flows together with the booth exhaust air arriving from above to a nozzle which accelerates air flow. In this nozzle, the through-flowing booth exhaust air is swirled with the water. As this happens, the overspray particles largely pass over into the water, such that the air leaves the wet separator in a substantially purified state and the paint overspray particles are located in the water, from which they may then be recovered or disposed of.
In known wet separators, a relatively large amount of energy is required to circulate the very large quantities of water which are necessary. Treating the rinsing water is costly due to the elevated use of paint-binding and detackifying chemicals and disposal of paint sludge. Furthermore, due to intimate contact with the rinsing water, the air absorbs a great deal of moisture which, when the air is recirculated, in turn results in elevated energy consumption for air treatment.
In contrast, in commercially known devices of the above-mentioned type separation is performed by dry methods in that the paint overspray particles entrained by the booth exhaust air are ionised as they flow past the electrode apparatus and, due to the electric field established between the separation surface and the electrode apparatus, migrate to the separation surface, on which they separate out. The paint overspray particles adhering to the separation surface may then for example be mechanically scraped off therefrom and conveyed away.
Such separators have a very effective cleaning action. However, if operation is to be continuous, constant care must be taken to ensure that a sufficiently strong electric field can form between the separation surface and the electrode apparatus, something which is only possible up to a certain layer thickness of paint overspray on the separation surface, since such a layer has an insulating action. The necessary continuous removal of the paint overspray from the separation surface is, however, associated with very considerable structural complexity and may be susceptible to breakdown.
The present invention is directed to resolving these and other matters.